1. Field of the Invention
The present invention relates to molding machines for use with gas-assisted injection molding processes.
2. Description of the Prior Art
Gas-assisted injection molding has been developed to permit an article to be molded with a hollow interior. In this process, a mold is provided with a cavity of the external shape of the article. Molding material is inserted into the cavity so that it fills the cavity and gas is then injected within the cavity to expel a portion of the molding material through an outlet. The material adjacent the walls of the mold remains and can then be pressurized to enhance the surface finish of the finished article. Thereafter, the mold is opened and the article ejected.
This arrangement has been commercially successful although some difficulties remain in the ejection and quality control monitoring of the molding process. With existing processes, the venting of material is controlled by a valve member that effectively seals the internal cavity provided in the molded article. In so doing, however, it is not possible through visual inspection to determine whether or not the material has been expelled from the interior of the molded article. Moreover, removal of the molded article and of the vented material is difficult.
It is therefore an object of the present invention to obviate or mitigate the above disadvantages.